Ternary-Responsive Field-Effect Transistors and Multilevel Memories Based on Asymmetrically Functionalized Janus Few-Layer WSe2

Hybrids composed of 2D transition metal dichalcogenides with stimuli-responsive molecules are prototypical components for the development of multifunctional field-effect transistors (FETs), whose output currents can be remotely controlled by external inputs. Herein, ternary-responsive FETs based on a few-layer WSe₂ are realized by decorating the two opposite surfaces of the 2D semiconductor with different stimuli-responsive molecules in an asymmetric fashion: the bottom surface is interfaced with a photochromic diarylethene film and the top surface with a ferroelectric poly(vinylidene fluoride–trifluoroethylene) layer. This novel Janus ternary device architecture shows superior functional complexity compared with normal mono-stimuli-responsive FETs. The synergy between the two molecularly induced effects enables the devices to respond orthogonally to an electric field and light irradiation, with an enhanced output current modulation efficiency of 87%. The 9 ferroelectric and 84 photo-generated states ensure 756 current levels in a single device. The over 10 cycles of cyclic endurance and more than 1000 h of retention time confirm the reliability of each state, implementing the demand for high-density non-volatile memories, as well as enriching the diversification in “More than Moore” technologies.     

Dynamical modeling of transport in MOS structures containing silicon nanocrystals for memory applications

A compact model that can be used to reproduce both quasi-static and dynamic characteristics of basic MOS cells with embedded Si-nc is presented. The structure is modeled through a device-like complex matrix of tunnel junctions, resulting in a time-dependent non-linear system of differential equations that is numerically solved, including calculation of the capacitance matrix, analytical tunneling expressions (direct and Fowler-Nordheim) for electrons/holes, and derivation of the effective tunneling area. The threshold evolution is calculated by monitoring the charge at each Si-nc as a function of time. The model is successfully validated against experimental data, showing its applicability to predict program/erase characteristics of nanocrystal memories as well as threshold voltage bit-to-bit dispersion as a consequence of geometrical non-uniformities in the nanocrystal layer position and/or gate areal coverage.     

Testing Address Decoder Faults in Two-Port Memories: Fault Models, Tests, Consequences of Port Restrictions, and Test Strategy

A two-port memory contains two duplicated sets of address decoders, which operate independently. Testing such memories requires the use of single-port tests as well as special two-port tests; the test strategy determines which tests have to be used. Many two-port memories have ports which are read-only or write-only; this impacts the possible tests for single-port and two-port memories, as well as the test strategy. In this paper the effects of interference and shorts between the address decoders of the two ports on the fault modeling are investigated. Fault models and their tests are introduced. In addition, the consequences of the port restrictions (read-only or write-only ports) on the fault models and tests are discussed, together with the test strategy.     

Calamitic Blatter Radicals for Large-Area Solution-Coated Resistive Memories

Radical molecules exhibit fast redox kinetics, are widely explored for data processing and energy storage. However, the insulating aliphatic matrix isolates the radical units, thus resulting in a weak charge transporting ability. Herein, calamitic Blatter radicals (CBR) with highly conductive [1]benzothieno[3,2-b]benzothiophene (BTBT) as the conjugated backbone are designed and synthesized. It is found that bistable redox character associated with large conjugated backbone allows these Blatter radical derivatives to be switched with ON/OFF ratio reaching 10⁶ and retention time exceeding 10⁴ s in solution processed devices. In addition, these radicals are unveiled to perform tunable, multi-mode field-responsive resistance behaviors, including write-once-read-many (WORM), FLASH, and dynamic random access memory (DRAM), by molecular engineering strategy. This finding provides fundamental understanding for charge transferring dynamics and redox-switching mechanism of radical molecules with respect to electronic applications.     

综合联想记忆神经网络的外积取等准则

本文提出了一个新的联想记忆设计准则，即外积取等准则，它具有外积和准则的所有优点。由外积取等准则设计出的联想记忆网络能够存储任意给定的训练模式，即对于训练模式的数目和它们之间相关性的强弱没有限制。外积取等准则可用来定量地评价记忆模式向量各分量对于记忆模式分类或识别的重要性。由外积取等准则设计出的网络的连接权值只取１、０或－１，因而网络易于光学实现。计算机实验结果充分说明了外积取等准则的有效性。     

Analysis of Imperfect Rephasing in Photon Echo-Based Quantum Memories

Over the last two decades, quantum memories have been intensively studied for potential applications of quantum repeaters in quantum networks. Various protocols have also been developed. To satisfy no noise echoes caused by spontaneous emission processes, a conventional two-pulse photon-echo scheme has been modified. The resulting methods include double-rephasing, ac Stark, dc Stark, controlled echo, and atomic frequency comb methods. In these methods, the main purpose of modification is to remove any chance of a population residual on the excited state during the rephasing process. Here, we investigate a typical Gaussian rephasing pulse-based double-rephasing photon-echo scheme. For a complete understanding of the coherence leakage by the Gaussian pulse itself, ensemble atoms are thoroughly investigated for all temporal components of the Gaussian pulse, whose maximum echo efficiency is 26% in amplitude, which is unacceptable for quantum memory applications.     

Alkoxide Derived SrBi2Ta2O9 Phase Pure Powder and Thin Films

Phase pure powder and thin films of the novel ferroelectric materials SrBi₂Ta₂O₉ (SBT) have been prepared using the organic precursors. The xero-gel formed was dried and characterized using TGA and DTA to determine the organic burn out and crystallization temperature of SBT. Powder X-ray diffraction was used systematically to check the crystallinity of SBT. Phase pure SBT powder was formed as low as 650°C and thin films at 600°C in comparison to other earlier reported work. SEM micrographs show a grain size of ≈0.1 μm and show crack free films with a film thickness of 2 μm.     

Three garnet compositions for bubble domain memories

The choice of magnetic garnet compositions for bubble memories is always a compromise dictated by the material requirements generated by the specifications on the memories. The three compositions reported, Y_2.62Sm_o.38Fe_3.85Ga_1.15O₁₂, Gd_2.lLu_O.9Fe_4.4Al_0.6O₁₂, and Y_l.92Sm_0.1Ca_0.98Fe_4.02Ge_0.98O₁₂, represent three examples of such a compromise. The first composition is excellent for use in circuits operating at 100 KH_z over a temperature range of -20° to 80°C. The second has a mobility up to 5000 cm/sec/0e and is capable of very high speed operation at the sacrifice of stability toward temperature. The third exhibits excellent stability toward temperature and has operated at 1 MHz but is compositionally more complex. Melt compositions for film growth and a summary of magnetic properties are presented for the three compositions. Factors to be weighed in composition selection for bubble domain memories are discussed.     

BE-TANOS: Feasibility and technology limitations

The aim of this work is to investigate the physical mechanisms behind the write/erase and retention performances of band gap engineering (BE) layers used as tunnel oxide in charge trap memory stack. The investigation of the BE layers alone will be completed with the analyses of its integration within a TANOS (TaN/Alumina/Nitride/Oxide/Silicon) stack, pointing out the correlation between electrical performance and reliability limits.Good write/erase/retention performances can be achieved with BE tunnel oxide by using silicon nitride layer integrated in SiO₂-Si₃N₄-SiO₂ stack, as long as all different mechanisms are taken into account in optimizing stack composition: hole injection which improves erase efficiency, charge trapping and de-trapping from the thin silicon nitride which causes program instabilities and initial charge loss which does not significantly impact long term retention. All these phenomena make very crucial the BE tunnel process control and difficult its use for multi-level application.